[Issue 16487] Add function to obtain the available disk space

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=16487

--- Comment #5 from Johan Engelen <jbc.engelen at gmail.com> ---
(In reply to b2.temp from comment #4)
> 2. returns -1 on failure. ulong.max: No way !!!

The return type is _unsigned_.
Throwing an exception is also a possibility.

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